What does radioactive decay involve?

Radioactive decay involves the transformation of unstable atomic nuclei into more stable forms, which is often accompanied by the release of high-energy particles. This process can include various types of emissions, such as alpha particles, beta particles, and gamma rays. The release of these particles is what characterizes radioactive decay, as the unstable nucleus seeks a more stable energy state by emitting energy and mass in the form of radiation.

In contrast, the other options focus on different processes. The conversion of energy to matter typically relates to particle-antiparticle pair production and does not describe decay. Combining nuclei of light elements refers to nuclear fusion rather than decay, and absorption of energy from surroundings is not a feature of radioactive decay, as the process is self-contained within the unstable atom's transformation. Therefore, the emphasis on the release of high-energy particles accurately captures the essence of radioactive decay.